Hello, friend!
I didn't see your question in time due to the sharing post you chose.
The HG8145V5 is a carrier-series ONT. To configure port forwarding, open the configuration page according to the following tab sequence.
Click Advanced Configuration > Forward Rules tab, and choose IPv4 Port Mapping. In the dialog box that is displayed, set the parameters related to port mapping.
For details about how to release the Ask for Help post, see: How to Quickly Seek Help-Forum
Thanks!